Public works and water crews clean up on Lausanne Avenue and Clayton Court after a river of mud rolled through a neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Public works and water crews clean up on Lausanne Avenue and...

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Resident Gualter Fontanilla waits for help from city crews to free his car from thick mud after a mudslide rolled through his neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Resident Gualter Fontanilla waits for help from city crews to free...

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Public works and water crews clean up on Lausanne Avenue after a river of mud rolled through a neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Public works and water crews clean up on Lausanne Avenue after a...

Image 4 of 15

Public works and water crews clean up on Lausanne Avenue and Clayton Court after a river of mud rolled through a neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Public works and water crews clean up on Lausanne Avenue and...

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Residents help public works and water crews dig cars out after a mudslide rolled through a neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Residents help public works and water crews dig cars out after a...

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Public works and water crews dig out cars stuck in mud after a mudslide rolled down Lausanne Avenue following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Public works and water crews dig out cars stuck in mud after a...

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Heavy machinery scoops up mud on Lausanne Avenue and Clayton Court after a mudslide rolled through a neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Heavy machinery scoops up mud on Lausanne Avenue and Clayton Court...

Image 8 of 15

Heavy machinery scoops up mud on Lausanne Avenue after mudslide rolled through a neighborhood following a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Heavy machinery scoops up mud on Lausanne Avenue after mudslide...

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Public works and water department crews operate heavy machinery in an effort to clean up the muddy river that coursed through a Daly City neighborhood in the early-morning hours.

Photo: Paul Chinn, The Chronicle

Public works and water department crews operate heavy machinery in...

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Police officers stand at the top of Lausanne Avenue while public works and water crews clean up a river of mud that rolled through a neighborhood after a water line break from a hilltop reservoir in Daly City, Calif. on Tuesday, Nov. 13, 2012.

Photo: Paul Chinn, The Chronicle

Police officers stand at the top of Lausanne Avenue while public...

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City workers survey the damage that was done when a water main under a hillside broke and sent 45,000 gallons of water into the neighborhood below.

Residents along a quiet Daly City street woke up to an alien world Tuesday after an aging water main broke and spewed 45,000 gallons of water down a sandy hill, caking the streets in a sea of silty brown mud.

Cars parked along the crest of Lausanne Avenue sat in several feet of mud as residents and city workers shoveled the gunk into bigger piles for front loaders to scoop up and plop into waiting dump trucks.

The suburban neighborhood looked as though Paul Bunyan had spilled his morning coffee all over the street, dregs included.

"We're flabbergasted," said Kelley Braas, lead groundskeeper with the city's parks department. "Everybody from our department and other departments is out here to help. ... This is major, major work."

The flood began just before 4:30 a.m. when a 25-foot-long segment of 8-inch cast iron pipe broke off and let loose a river of water from the city-owned water tank perched on top of a nearby hill, said Matt Lucett, a spokesman for the North County Fire Department.

Emmanuel Romero, 28, was awake at his house at the foot of the hill when he heard an unfamiliar sound in the wee hours of the morning.

"I heard rushing water flowing by the house, but there's no river out here, so I thought maybe it was rain but I looked outside and there were no clouds," Romero said. "I checked again outside and saw water and mud covering a wide area so I called 911. But I didn't see the full damage until the sun came up and I looked outside and saw all the mud. ... We were lucky."

Romero's house, like every other house in the neighborhood, was surprisingly unharmed. No flood waters or debris damaged homes in the area, though cars might be a different story once they're cleared from the mud.

"The mud settled below the tailpipe, but I'm not sure what kind of damage it got at the peak," Romero said. "I guess this is what insurance is for."

The sudden river of water left a deep crevasse in the hillside, about 20 feet wide and just as deep. Officials don't yet know how much mud flowed down the hill but it was enough to smother a nearby park several feet deep and streak down Lausanne Avenue for several blocks.

Twelve houses just below the hill were evacuated for five hours while engineering crews inspected the mudslide to make sure it was stable and posed no threat of a landslide. About 100 houses had minor inconveniences because of the main break, including low water pressure.

The 78-year-old pipe broke about 100 yards away from the 970,000-gallon water tank, which serves the southeast part of Daly City, said Patrick Sweetland, director of water and wastewater resources. Water service was restored in the neighborhood on Tuesday from another source, Sweetland said.

"We suspect (the break) had a lot to do with the pipe's age," Sweetland said.

Cast iron was more common in 1934, when the pipe was installed. Now, the city uses ductile iron pipes, which are stronger, Sweetland said.

The cleanup effort along the street took all day Tuesday, officials said. They brought in four vacuum trucks, five backhoes, eight dump trucks and four small front loaders to scoop away the layers of mud, grass and other debris, Sweetland said.

After the street is cleared, crews will spend several more days clearing out the parks and other areas, Sweetland said. The mud is being trucked away to a recycling center in Brisbane.